剑指 Offer 32 - III. 从上到下打印二叉树 III

剑指 Offer 32 - III. 从上到下打印二叉树 III

思路：
参考
代码：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
    if(!root) return {};
    vector<vector<int>> res;
    queue<TreeNode*> q;
    q.push(root);
    while(q.size()){
        int len = q.size();
        vector<int> path;
        while(len--){
            auto t = q.front();
            q.pop();
            path.push_back(t->val);
            if(t->left) q.push(t->left);
            if(t->right) q.push(t->right);
        }
        res.push_back(path);
    }
    
    for(int i = 0; i < res.size(); i++){
        if(i % 2) reverse(res[i].begin(),res[i].end());
    }
    
    return res;
    };
};